The present invention relates to retractable cover or tarping systems, and especially systems configured for use on the bed of a trailer or other hauling vehicle. More specifically, the invention concerns devices for locking the ends of the retractable tarping system.
Flat bed trailers are used to haul a variety of goods ranging from large heavy articles such as machinery to palletized goods. It is desirable, particularly with regard to weather sensitive goods, to provide a cover to protect a load during transit. Various types of cover systems have been used ranging from simple tarps held in place with cargo straps and tie downs to retractable tarp systems that cover and protect the entire trailer bed from weather and debris.
One such retractable tarp system is the CONESTOGA® tarp cover system manufactured and sold by Aero Industries of Indianapolis, Ind. Details of this type of cover system are disclosed in the U.S. Pat. No. 4,711,484, issued on Dec. 8, 1987, U.S. Pat. No. 4,902,064, issued on Feb. 20, 1990, and U.S. Pat. No. 5,538,313, issued on Jul. 23, 1996, all of which are owned by the assignee of the present invention. The disclosures of the '484, '064 and '313 Patents are incorporated herein by reference. The CONESTOGA® tarp system was developed to provide a tarp cover system that not only effectively encloses the cargo area but also protects or seals the tarp cover deployment system. The CONESTOGA® system includes a wheel and track deployment system that is supported at the outside edges of the trailer. In this manner, the entire trailer bed is under cover.
With flexible cover systems like the CONESTOGA® system, it is important to keep the tarp cover in tension. The tensioned tarp more effectively seals the cargo area from the elements, and resists flapping due to wind and road vibration. In the typical extendable tarp system, the tarp cover is stretched slightly on deployment and latched to front and rear bulkhead structures.
However, the typical tarp cover stretches and becomes loose over time. This leads to billowing and flapping of the cover, particularly at the end sections, which accelerates wear and deterioration of the tarp cover if not addressed. The '064 patent addresses this problem somewhat in the design of the tarp bow guide tracks. The rear portion of each guide track is inclined downwardly, so that as the rearmost bow carrier enters this part of the track, the bow which is attached to this carrier “leans” back and away from the front of the trailer, thereby pulling the tarp taught. Although this approach is automatic in that no special action by the driver of the vehicle is necessary, the amount of tightening that it provides is limited.
The '313 Patent provides another solution integrated into mechanisms for locking the front and rear of the tarping system to either the flat bed or a bulkhead structure that is fixed to the flat bed. Certain details of the system disclosed in the '313 Patent are depicted in FIGS. 1-3. In particular, a retractable cover system 10 is mounted on a flat bed 12. Guide rails 14 are mounted to the sides of the bed 12 and a front bulkhead 17 is mounted to the front of the bed. The cover system 10 is defined by a plurality of intermediate bows 20 and uplift bows 21 that support a cover or tarpaulin 11 (FIG. 2) attached thereto. The bows 20, 21 are supported by carriers 22 that are configured to ride within the guide rails 14.
As shown in FIG. 1, the retractable cover system 10 may include a front bow structure 23 and an opposite rear bow structure 25, both of which are attached to the tarp 11. The rear bow structure 25 is configured to carry a rear door 26 (FIG. 9) that may be a hinged door, as depicted in the figure, or a flap that is rolled upward onto the top of the tarp 11 in a known manner.
The cover system 10 is provided with a front locking mechanism 27 that engages the front bow structure 23 to the front bulkhead 17. A rear locking mechanism 28 is also provided for locking the rear bow structure 25 to the flat bed 12. Details of the front locking mechanism 27 disclosed in the '313 Patent are illustrated in FIG. 2 and are incorporated herein by reference. The mechanism 27 includes a movable component supported on a front bulkhead frame member 30. The front bow structure includes a front beam 24 that carries a plurality of locking members 35 fixed thereto. The mechanism 27 includes a pair of locking bars 32 mounted at either side of the bulkhead 17 so that locking bars can be vertically translated. The locking bars carry a plurality of latches 33 that are configured to engage a corresponding locking pin 35 as the locking bars 32 are moved downward. The bars are moved by rotation of a lifting shaft 37. A hand crank 38 engages the shaft 37 from the outside of the bulkhead 17.
In use, the vehicle operator slides the front bow structure 23 toward the front bulkhead 17 until the locking pins 35 are in proximity to the corresponding latches 33. With the front bow structure so position, the vehicle operator then rotates the hand crank 38 to rotate the lifting shaft and pull the locking bars 32 down until the latches 33 engage the pins 35. On problem with this front locking mechanism 27 is that it can sometimes be cumbersome to keep the front bow structure in the proper orientation relative to the front bulkhead so that the latches 33 uniformly engage all of the locking pins 35. Another detriment is that the locking bars 32 and lifting shafts 37 are open to the cargo space within the front bulkhead 17. Thus, the locking mechanism is susceptible to damage as cargo is loaded onto the flat bed 12. Moreover, the mechanism occupies valuable cargo storage space. There is therefore a need for an improved locking mechanism that avoids these problems when used to lock the retractable cover to the front bulkhead.
Details of the rear locking mechanism 28 are shown in FIG. 3 and are incorporated herein by reference. The mechanism 28 includes a receptacle 40 that is fixed to the flat bed 12. A locking bar 42 includes a locking end 43 that is configured to be received within the receptacle 40. The locking end 43 extends through a slot 46 in a bottom frame element 45 of the rear bow structure 25 so that the mechanism 28 is generally contained within the envelope of the bow structure. The locking bar 42 is pivotably connected to a cam element 47, which is itself pivotably connected to the bow structure 28 at a pivot mount 48. A manual crank 49 may be engaged to the cam element 47 at either side of the pivot mount 48. Rotation of the crank 49 rotates the cam 47, which then pivots the locking bar 42 into locking engagement with the receptacle 40. The cam 47 is configured to exert a tensioning force on the rear bulkhead structure after the locking end 43 is engaged within the receptacle, to thereby apply tension to the tarp 11. In other words, the rear locking mechanism 28 is configured to not only lock the rear bow structure 25 to the flat bed 12, but to also tension the tarp. While this rear locking mechanism 28 provides means for tensioning the tarp, the mechanism is limited to a certain range of tarp stretching. As explained above, most tarps stretch over time, so that the overall length of the retractable cover system 10 necessarily increases from continued use. While the cam 47 can account for some tarp stretching, it generally depends upon tension in the tarp for its functionality. If the tarp has stretched too much, it cannot provide enough tension force for the full range of movement of the cam. Consequently, there is a need for a locking mechanism that is capable of a significant range of adjustment to control tarp tension while locking a cover system bow structure the flat bed or trailer.